Solar energy systems have emerged as a viable source of renewable energy over the past two or three decades, and are now widely used in a variety of industrial and domestic applications. Such systems are designed to collect the solar energy and to convert it into either electrical power or thermal energy. The optimum solar energy is obtained when sun rays are incident vertically to the transforming part of solar power systems. Examples include solar thermal system and photovoltaic system. Both concentrated solar collector and photovoltaic collector require the use of solar trackers to increase the area exposed to the direct radiation of the sun.
The solar trackers can be divided into single-axis trackers and dual-axis trackers by taking into account the mechanical characteristics. Since dual-axis systems are able to obtain an optimal tracking of the sun, they are more popular in all the types of concentrated solar technologies, with the exception of the trough-style system. However, the predominant dual-axis trackers are commonly designed based on serial architectures where two revolute joints ensure the rotational DOFs. The trackers require a very stout pole drilled into the ground to support normal loading. In all cases, the pole height is at least half of the panel height above the ground so that the tracker can orient toward the sun at low elevation angles. Being serial, their main disadvantage is the need of a heavy structure in order to keep rigidity at levels sufficient to sustain solar panel loads. The serial tracker is a large-torque mechanism due to the cantilever beam architecture. The servomotors cannot provide such large torques hence reducers with large reduction ratio are needed. These drive units contain multiple sets of gears that must be designed to handle very large moments and loads. Therefore, the conventional serial tracker is a heavy duty equipment. Also, they are often fitted with heavy counter balances. These result in larger actuator requirements making their power consumption far from optimal.
Minimizing the energy consumption is a very important design requirement for solar trackers. Compared with classical serial mechanisms, parallel mechanisms provide a number of advantages including higher payload to weight ratio, better dynamics and larger stiffness. If parallel mechanisms are utilized to design solar trackers, it is possible to reduce the driving torque, scale down the dimensions of the mounting and reduce the complexity of the system in terms of the number of its components and its assembly. These can reduce the energy consumption. A few solar trackers with parallel mechanisms have been developed. However, the main drawbacks of parallel kinematic solar trackers are small workspace to installation space ratio, as well as the presence of singular configurations within the workspace. Due to the previously mentioned advantages of parallel mechanisms, the parallel kinematic solar trackers have vast potentials for future development if the small workspace problem can be overcome.
By taking both the advantages of traditional solar tracker and parallel mechanism into account, this invention designs a new generation of solar trackers. Compared with other solar trackers, this invention possesses several advantages as simple structure, enough workspace to track the sun, small torque, high stiffness and low energy consumption.